A newly discovered malware variant dubbed Coyote is making headlines in cybersecurity circles after researchers revealed its advanced capabilities to bypass defenses and harvest sensitive credentials from Windows systems. Discovered by security analysts at Trend Micro, Coyote has been identified as a significant evolution of the well-known open-source Brute Ratel C4 (BRC4) post-exploitation toolkit.
Coyote: A Sophisticated Offshoot of Brute Ratel
According to Trend Micro’s technical brief published earlier this month, Coyote builds on the stealth and modularity of Brute Ratel while integrating new evasion and credential-stealing techniques. It reportedly leverages DLL sideloading—a common tactic used by threat actors to disguise malicious payloads—as a primary delivery method.
Unlike typical malware strains, Coyote appears to focus heavily on post-compromise activities. It exhibits the capability to dump LSASS (Local Security Authority Subsystem Service) memory, allowing it to extract credentials directly from Windows systems without immediately triggering antivirus alarms. It also uses named pipes for internal communication, enhancing its stealth within infected environments.
Delivery Method and Attack Vector
Trend Micro’s analysis traced a recent Coyote infection to a trojanized version of OneDriveSetup.exe, which sideloads a malicious DLL to gain execution. Once deployed, Coyote uses techniques aligned with advanced persistent threat (APT) actors, including defense evasion methods such as disabling Event Tracing for Windows (ETW) and obfuscating its command-and-control (C2) traffic.
Attribution and Scope
So far, Coyote has not been attributed to a known threat group, but its advanced functionality suggests it may be in use by professional cybercrime syndicates or state-aligned actors. The malware is not yet widespread but is under close monitoring due to its potential for rapid adoption and adaptation.
Trend Micro researchers stated:
“Coyote demonstrates how open-source red-teaming tools can be weaponized and evolved by malicious actors. It reflects an ongoing trend where legitimate penetration testing frameworks are turned into advanced malware variants.”
Mitigation and Recommendations
Security experts advise organizations to adopt a defense-in-depth strategy, including the following measures:
- Monitor for suspicious DLL sideloading activity.
- Harden LSASS against memory access by using Credential Guard or similar tools.
- Ensure behavioral detection systems are up to date to recognize named pipe misuse and other indicators of compromise.
- Regularly audit endpoint activity for signs of lateral movement or unusual memory access patterns.
Conclusion
Coyote underscores the blurred lines between red-teaming tools and real-world malware. As attackers grow more adept at repurposing legitimate software, organizations must increase their vigilance and invest in proactive detection and response strategies.
Sources:
- Trend Micro Threat Research
- BleepingComputer
- SecurityWeek
- MITRE ATT&CK Framework